The present invention generally relates to load bearing structures such as buildings, bridges, etc., and more particularly to a method of reinforcing a column positioned proximate a blocking structure such as a wall or spandrel beam.
Building structures are often made up of reinforced concrete columns. For many years, reinforced concrete columns were internally reinforced with ductile and high tensile strength material, such as steel rebar, primarily along their vertical (longitudinal) axes. Because such structures typically experience loading only in the vertical direction, the reinforcement of structural columns was thought to be exclusively needed along that axis. However, long experience has shown that in the event of an earthquake or a tremor, load bearing structures experience non-normal loading conditions, including particularly lateral loading. Under such non-normal loading conditions, vertically oriented columns are subjected to shearing. If the columns are not properly strengthened to prevent the formation of shear cracks, they may catastrophically fail. Newer structures have concrete columns that are reinforced against lateral (non-normal) loading conditions. However, many older structures remain that do not have reinforcement against non-normal loading.
In response to these risks, structures not originally designed and built to withstand non-normal loading conditions have been retrofitted to improve the shear capacity of their original columns. Many of the known methods of retrofitting reinforced concrete columns are unduly expensive or severely limit the use of the structure while they are being performed. One less expensive method of reinforcing concrete columns to improve their shear capacity and ductility involves confining the column in high strength fiber reinforced polymer. While this method is less time consuming, costly, and disruptive than other known methods, it is important for the best results that the column can be truly confined in the fibrous sheet material, that is, wrapped in fibrous sheets around its entire perimeter.
In many instances, a blocking structure, such as a spandrel beam or a wall attached directly to a column, makes it impossible to wrap sheet material completely about the column. In such instances, the column cannot be as effectively wrapped in fibrous sheets to achieve reinforcement through confinement without separating the column from the blocking structure to access its entire perimeter. The joints between columns and blocking structures are often critical to the structural integrity of load bearing structures. Separating blocking structures from the columns to which they are joined is an expensive proposition. It would require extensive demolition and would be highly disruptive to the ordinary use of the load bearing structure. In some cases, it may not even be possible for the load bearing structure to withstand the required demolition.